Poisson, SiméOn Denis (1781–1840)

Siméon Denis Poisson was born in Pithiviers, France. In 1825, he was awarded the title Baron, and in 1837, Peer of France.

The story is told that when Poisson was a child, his nanny once suspended him from a nail to protect him from animals prior to leaving him to conduct household errands. In swinging back and forth to release himself, he became interested in the properties of the pendulum, which he later studied extensively.

His mathematical talents were first noticed by Adrien-Marie Legendre (1752–1833) when Poisson was only 17. With Legendre's support, Poisson published a paper on finite differences in Recueil de Savants Étranges when he was only 18.

Poisson graduated from École Polytechnique. His teachers were Joseph Louis Lagrange (1736–1813) and Pierre Simon Laplace (1749–1827). He accepted a position at Polytechnique and rose through the ranks as Lecturer (Deputy Professor) in 1802, Professor (1806), and Examiner (1816). In 1808, he gained an appointment as Astronomer at Bureau des Longitudes, and he obtained a joint appointment as Chairman of Mechanics at the Faculté des Sciences in 1809. He was elected to the physics section of the Institut National des Sciences et des Arts (Académie des Sciences) in 1812. He became an Examiner for the École Militaire in 1815.

He published about 400 works, most of which appeared in Journal de l'École Polytechnique, Mémoires[Page 772]de l'Académie, and Connaissance des Temps. Poisson published in applied subjects, such as heat, celestial mechanics, and magnetism. His name is associated with the Poisson integral (potential theory), Poisson ratio (elasticity), and Poisson constant (electricity). Among his most important works are the Traité de Méchanicque, with Volume 1 published in 1811 and Volume 2 published in 1833. This masterpiece is remarkable considering Poisson was never involved in conducting experiments.

He also published extensively in pure mathematics. His name is associated with Poisson brackets (differential equations). His major work in probability theory was Recherches sur la Probabilité de Jugements, published in 1837, in which he coined the phrase “law of large numbers,” derived from the work of Bernoulli. The major implication is that the binomial distribution tends toward the normal distribution as the number of trials increases, but as the number of successes decreases, the limit becomes the Poisson distribution.

Poisson was a gifted mathematician and teacher. His students included Michel Chasles (1793–1880), Gustav Peter Lejeune Dirichlet (1805–1859), and Joseph Liouville (1808–1882), who led the next generation's mathematicians.